Implantable heart assist system

ABSTRACT

An extracardiac pumping system for supplementing the circulation of blood through a patient without any component thereof being connected to the patient&#39;s heart, and method of using same. The extracardiac system comprises a pump implanted subcutaneously at or about the patient&#39;s groin in a minimally-invasive procedure, wherein the pump is powered by a battery, and means for charging the battery extracorporeally, wherein the pump draws blood through an inflow conduit fluidly coupled to the patient&#39;s femoral artery via a subcutaneous anastomosis connection, and discharges blood through an outflow conduit fluidly coupled to a peripheral artery that stems from the patient&#39;s aortic arch via a subcutaneous anastomosis connection. The pump may be operated continuously or in a pulsatile fashion, synchronous with the patient&#39;s heart, thereby potentially reducing the pumping load on the heart.

RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 09/166,005 now U.S.Pat. No. 6,200,260 B1 filed on Oct. 2, 1998, which was based upon aprovisional application filed Oct. 9, 1997, U.S. Provisional ApplicationSerial No. 60/061,434, which is incorporated herein in its entirety byreference.

FIELD OF THE INVENTION

The present invention relates generally to a system for assisting theheart and, in particular, to an extracardiac pumping system and a methodfor supplementing the circulation of blood through the patient using aminimally invasive procedure.

BACKGROUND OF THE INVENTION

During the last decade, congestive heart failure (CHF) has burgeonedinto the most important public health problem in cardiovascularmedicine. As reported in Gilum, R. F., Epidemiology of Heart Failure inthe U.S., 126 Am. Heart J. 1042 (1993), four hundred thousand (400,000)new cases of CHF are diagnosed in the United States annually. Thedisorder is said to affect nearly 5 million people in this country andclose to 20 million people worldwide. The number of hospitalizations forCHF has increased more than three fold in the last 15 years.Unfortunately, nearly 250,000 patients die of heart failure annually.According to the Framingham Heart Study, the 5-year mortality rate forpatients with congestive heart failure was 75 per cent in men and 62 percent in women (Ho, K. K. L., Anderson, K. M., Kannel, W. B., et al.,Survival After the Onset of Congestive Heart Failure in Framingham HeartStudy Subject, 88 Circulation 107 (1993)). This disorder represents themost common discharge diagnosis for patients over 65 years of age.Although the incidence of most cardiovascular disorders has decreasedover the past 10 to 20 years, the incidence and prevalence of congestiveheart failure has increased at a dramatic rate. This number willincrease as patients who would normally die of an acute myocardialinfarction (heart attack) survive, and as the population ages.

CHF manifests itself primarily by exertional dyspnea (difficult orlabored breathing) and fatigue. Three paradigms are used to describe thecauses and therapy of CHF. The first views this condition in terms ofaltered pump function and abnormal circulatory dynamics. Other modelsdescribe it largely in terms of altered myocardial cellular performanceor of altered gene expression in the cells of the atrophied heart. Inits broadest sense, CHF can be defined as the inability of the heart topump blood throughout the body at the rate needed to maintain adequateblood flow, and many of the normal functions of the body.

To address CHF, many types of cardiac assist devices have beendeveloped. A cardiac or circulatory assist device is one that aids thefailing heart by increasing its pumping function or by allowing it acertain amount of rest to recover its pumping function. Becausecongestive heart failure may be chronic or acute, different categoriesof heart assist devices exist. Short of a heart transplant, at least twotypes of chronic heart assist systems have been developed. One typeemploys a full or partial prosthetic connected between the heart and theaorta, one example of which is commonly referred to as a LVAD—LeftVentricular Assist Device. With reference to FIG. 1 herein, one exampleof a LVAD 2 is shown. The LVAD comprises a pump and associated valves 4that draws blood directly from the apex of the left ventricle 6 anddirects the blood to the aortic arch 8, bypassing the aortic valve. Inthis application, the left ventricle stops functioning and does notcontract or expand. The left ventricle becomes, in effect, an extensionof the left atrium, with the LVAD 2 taking over for the left ventricle.The ventricle, thus, becomes a low-pressure chamber. Because the intentis to take over for the left ventricle, the LVAD operates by pumpingblood at cardiac rates. With an LVAD, oxygenated blood circulation isestablished sufficient to satisfy the demand of the patient's organs.

Another type of chronic heart assist system is shown in U.S. Pat. No.5,267,940 to Moulder. Moulder describes a pump implanted into theproximal descending aorta to assist in the circulation of blood throughthe aorta.

In addressing acute CHF, two types of heart assist devices have beenused. One is counterpulsatory in nature and is exemplified by anintra-aortic balloon pump (IABP). With an IABP, the balloon is collapsedduring isovolumic contraction, providing a reduced pressure againstwhich the heart must pump blood, thereby reducing the load on the heartduring systole. The balloon is then expanded, forcing bloodomnidirectionally through the arterial system. Another example of thisfirst type employs one or more collapsible chambers in which blood flowspassively into the chamber during systole, as is shown in U.S. Pat. No.4,240,409 to Robinson et al. The chamber is then collapsed and the bloodforcibly returned to the aorta. These devices simulate a chamber of theheart and depend upon an inflatable bladder to effectuate pumpingaction, requiring an external pneumatic driver.

A second type of acute assist device utilizes an extracorporeal pump,such as the Biomedicus centrifugal pump, to direct blood through thepatient while surgery is performed on the heart. In one example,described in U.S. Pat. No. 4,968,293 to Nelson, the heart assist systememploys a centrifugal pump in which tie muscle of the patient is mountedto add pulsatility to the blood flow. The Nelson device is used tobypass a portion of the descending aorta.

Another device, shown in U.S. Pat. No. 4,080,958 to Bregman et al.,utilizes an inflatable and collapsible bladder to assist in bloodperfusion during heart trauma and is intended to supplement aconventional heart-lung machine by imparting pulsatile actuation. In theprimary embodiment disclosed in Bregman, the balloon is controlled tomaintain sufficient pressure at the aortic root during diastole toensure sufficient blood perfusion to the coronary arteries. In analternative embodiment, a low resistance outlet from the aorta to theinferior vena cava is provided to reduce the aortic pressure duringsystole, thus, reducing the hemodynamic load on the left ventricle.

Other devices, such as that shown in U.S. Pat. No. 4,034,742 to Thoma,depend upon interaction and coordination with a mechanical pumpingchamber containing a movable pumping diaphragm. These devices areintended primarily for application proximate the heart and within thepatient's thorax, requiring major invasive surgery.

Many CHF devices are acutely used in the perioperative period. Forexample, U.S. Pat. No. 4,995,857 to Arnold discloses a perioperativedevice to pump blood at essentially cardiac rates during surgery whenthe heart has failed or has been stopped to perform cardiac surgery. TheArnold system temporarily replaces the patient's heart and lungtemporarily and pumps blood at cardiac rates, typically 5 to 6liters/min. Like all systems that bypass the heart and the lungs, anoxygenator is required. Of course, with any system that includes anoxygenator, such as the conventional heart-lung machine, the patientcannot be ambulatory.

With early IABP devices, a polyurethane balloon was mounted on avascular catheter, inserted into the femoral artery, and positioned inthe descending aorta just distal to the left subclavian artery. Theballoon catheter was connected to a pump console that pumped helium orcarbon dioxide into the balloon during diastole to inflate it. Duringisovolumic contraction, i.e., during the brief time that the aorticvalve is closed and the left ventricle continues to contract, the gasused to actuate the balloon was rapidly withdrawn to deflate theballoon. This reduced the pressure at the aortic root when the aorticvalve opened. In contrast, during diastole, the balloon was inflated,causing the diastolic pressure to rise and pushing the blood in theaorta distally towards the lower part of the body (on one side of theballoon) and proximally toward the heart and into the coronary arteries(on the other).

The major advantage in such a counterpulsation device was systolicdeflation, which lowered the intra-aortic volume and pressure, reducingboth afterload and myocardial oxygen consumption. In other words, whenthe balloon is inflated, it creates an artificially higher pressure inthe aorta, which has the ancillary benefit of greater perfusion throughthe coronary arteries. When the balloon deflates, just before the aorticvalve opens, the pressure and volume of the aorta decrease, relievingsome of the hemodynamic burden on the heart. These physiologic responsesimproved the patient's cardiac output and coronary circulation,temporarily improving hemodynamics. In general, counterpulsation with anIABP can augment cardiac output by about 15%, this being frequentlysufficient to stabilize the patient's hemodynamic status, which mightotherwise rapidly deteriorate. When there is evidence of more efficientpumping ability by the heart, and the patient has moved to an improvedclass of hemodynamic status, counterpulsation can be discontinued, byslowly weaning while monitoring for deterioration.

Until 1979, all IABP catheters were inserted via surgical cutdown,generally of the femoral artery. Since then, the development of apercutaneous IABP catheter has allowed quicker, and perhaps safer,insertion and has resulted in more expeditious institution of therapyand expansion of clinical applications. Inflation and deflation of theballoon, however, requires a pneumatic pump that is sufficiently largethat it must be employed extracorporeally, thereby restricting thepatient's movements and ability to carry out normal, daily activities.IABP devices are, thus, limited to short term use, on the order of a fewdays to a few weeks.

As discussed above, a variety of ventricular assist pumping mechanismshave been designed. Typically associated with LVADs are valves that areused in the inlet and outlet conduits to insure unidirectional bloodflow. Given the close proximity of the heart, unidirectional flow wasnecessary to avoid inadvertent backflow into the heart. The use of suchvalves also minimized the thrombogenic potential of the LVAD device.

Typically, the pump associated with older LVADs was a bulky pulsatileflow pump, of the pusher plate or diaphragm style, such as thosemanufactured by Baxtor Novacor or TCI, respectively. Given that the pumpwas implanted within the chest and/or abdominal cavity, major invasvesurgery was required. The pumps were typically driven through apercutaneous driveline by a portable external console that monitors andreprograms functions.

Alternatively, rotary pumps, such as centrifugal or axial pumps, havebeen used in heart assist systems. With centrifugal pumps, the bloodenters and exits the pump practically in the same plane. An axial pump,in contrast, directs the blood along the axis of rotation of the rotor.Inspired by the Archimedes screw, one design of an axial pump has beenminiaturized to about the size of a pencil eraser, although otherdesigns are larger. Despite its small size, an axial pump may besufficiently powerful to produce flows that approach those used witholder LVADs. Even with miniaturized pumps, however, the pump istypically introduced into the left ventricle through the aortic valve orthrough the apex of the heart, and its function must be controlled froma console outside the body through percutaneous lines.

All of these heart assist systems referred to above serve one or both oftwo objectives: (1) to improve the performance of a patient'soperative-but-diseased heart from the minimum, classified as NYHAC ClassIV, to practically normal, classified as I or 0; or (2) to supplementoxygenated blood circulation through the patient to satisfy organ demandwhen the patient's heart is suffering from CHF. With such systems,extreme pumping and large amounts of energy, volume, and heatdissipation are required.

Many of these heart assist systems have several general features incommon: 1) the devices are cardiac in nature; i.e., they are placeddirectly within or adjacent to the heart, or within one of the primaryvessels associated with the heart (aorta), and are often attached to theheart and/or aorta; 2) the devices attempt to reproduce pulsatile bloodflow naturally found in the mammillary circulatory system and,therefore, require valves to prevent backflow; 3) the devices are drivenfrom external consoles, often triggered by the electrocardiogram of thepatient; and 4) the size of the blood pump, including its associatedconnectors and accessories, is generally unmanageable within the anatomyand physiology of the recipient. Due to having one or more of thesefeatures, the prior art heart assist devices are limited in theireffectiveness and/or practicality. It would be advantageous to employ aheart assist system that avoids major invasive surgery and also avoidsthe use of peripheral equipment that severely restricts a patient'smovement.

SUMMARY OF THE INVENTION

The object of the present invention is to address the aspect of CHF thatresults from altered pump function and abnormal circulatory dynamicswhile overcoming the limitations of prior art heart assist systems.Without functioning as a bypass to one or more of a patient's organs,the present invention comprises an extracardiac pumping system forsupplementing the circulation of blood through the patient without anycomponent thereof being connected to the patient's heart or primaryvessel. Thus, it is extracardiac in nature. With the ability to beapplied within a minimally invasive procedure, the present inventionsignificantly improves the condition of the patient suffering from CHF,resulting in the patient feeling much better, even where CHF continues.An ancillary but important benefit of the present invention is theability to apply the present invention in such a way as to also reducethe pumping load on the heart, thereby potentially permitting the heartto recover during use. With the present invention, no bulky pump, valvesor oxygenator are required, and no thoracic invasion with major cardiacsurgery is required. Indeed, a significant advantage of the presentinvention is its simplicity while achieving extraordinary results inimproving the condition of a patient suffering from CHF.

The extracardiac system of the present invention preferably comprises arotary pump configured to pump blood through the patient at subcardiacrates; i.e., at a flow rate significantly below that of the patient'sheart. Other types of pumps may be effective as well. Pumping the bloodtends to revitalize the blood to a certain extent by imparting kineticand potential energy to the blood discharged from the pump. Importantly,the preferred pump for the present invention pumping system is one thatrequires a relatively low amount of energy input, when compared to priorart pumps designed to pump at cardiac rates. The pump may be implantedor not, depending upon the capability, practicality, or need of thepatient to be ambulatory.

The present system also comprises an inflow conduit fluidly coupled tothe pump, to direct blood to the pump from a first peripheral bloodvessel, and an outflow conduit fluidly coupled to the pump, to directblood from the pump to a second peripheral blood vessel. The connectionof the inflow and outflow conduits to the blood vessels is performedsubcutaneously; not so deep as to involve major invasive surgery. Inother words, minimally subdermal. This permits application of theconnections in a minimally-invasive procedure. Preferably, theconnections to the blood vessels are just below the skin or just belowthe first layer of muscle, depending upon the blood vessels at issue orthe location of the connection, although slightly deeper penetrationsmay be necessary for some patients.

In one embodiment of the extracardiac system, the pump is a continuousflow and/or pulsatile pump that is implantable and is used to connecttwo peripheral arteries, such as the femoral artery at the inflow andthe left axillary artery at the outflow, although other peripheral bloodvessels are contemplated, including other arteries and/or veins, as wellas any singular and/or cumulative combination thereof. An alternativeembodiment employs a rotary pump that is controllable in a synchronouscopulsating or counterpulsating fashion, or in some out-of-phaseintermediate thereof. In one application, it is contemplated that thepresent invention may be applied such that the heart experiences areduced pressure at the aortic root during systole, thus reducing thehemodynamic burden on the heart and, thus, permitting the heart torecover.

It is contemplated that, where the entire system of the presentinvention is implanted, that it be implanted subcutaneously without theneed for major invasive surgery and, preferably, extrathoracically. Forexample, the pump may be implanted in the groin area, with the inflowconduit attached to the femoral or iliac artery proximate thereto andthe outflow conduit attached to the axillary artery proximate theshoulder. It is contemplated that the outflow conduit be applied bytunnelling it under the skin from the pump to the axillary artery. Whereimplanted, the pump is preferably powered by an implantable battery thatmay be recharged externally by an RF induction system or replacedperiodically.

The present invention also comprises a method for supplementing thecirculation of blood in the patient and potentially reducing the pumpingload on the heart of a patient without connecting any component to thepatient's heart. The inventive method comprises the steps of implantinga pump configured to pump blood at volumetric rates that are on averagesubcardiac, wherein the pump has an inflow and outflow conduit attachedthereto; connecting a distal end of the inflow conduit to the firstperipheral blood vessel with a minimally-invasive surgical procedure topermit the flow of blood to the pump from a first peripheral bloodvessel of the patient; implanting the inflow conduit subcutaneously;connecting a distal end of the outflow conduit to the second peripheralblood vessel with a minimally-invasive surgical procedure to permit theflow of blood away from the pump to a second peripheral blood vessel ofthe patient; and operating said pump to perfuse blood through thepatient's circulatory system. In one specific application, the pump iscapable of synchronous control wherein the step of operating the pumpincludes the steps of beginning discharge of blood out of the pumpduring isovolurnic contraction and discontinuing discharge of blood whenthe aortic valve closes following systole. Depending upon the patientand the specific arrangement of the present system, this specific methodresults in reduced after-load on the heart while also supplementingcirculation. For example, in one embodiment, the first and second bloodvessels are the femoral and axillary arteries, respectively.

In an alternative method of applying the present invention, the pump isnot implanted and the inflow and outflow conduits are connected to thefirst and second blood vessels percutaneously, using a readily-removableconnector, such as a cannula, to connect the distal ends of each conduitto the blood vessels.

An important advantage of the present invention is that it utilizes thebenefits of an IABP, without the requirement of extracorporeal equipmentor the need to have a balloon or similar implement partially obstructinga blood vessel. The present invention thus offers simplicity andlong-term use.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will now bedescribed with reference to the drawings, which are intended toillustrate and not to limit the invention.

FIG. 1 is a schematic view of a cardiac assist device, known as a leftventricular assist device, showing a bypass from the apex of the leftventricle to the aortic arch;

FIG. 2 is a schematic view of a first embodiment of the presentinvention, shown applied to a patient's circulatory system.

FIG. 3 is a schematic view of a second embodiment of the presentinvention, shown applied to a patient's circulatory system.

FIG. 4 is a schematic view of a variation of the first embodiment ofFIG. 2 shown implanted into a patient;

FIG. 5 is a schematic view of a third embodiment of the presentinvention, shown applied to a patient's circulatory system.

FIG. 6 is a schematic view of a fourth embodiment of the presentinvention, shown applied to a patient's circulatory system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings provided herein, a more detailed descriptionof the embodiments of the present invention is provided below. It shouldbe noted, however, that while some embodiments have all of theadvantages identified herein, other embodiments may only realize somebut not all of the advantages.

The present invention provides a heart assist system that isextracardiac in nature. In other words, the present inventionsupplements blood perfusion, without the need to interface directly withthe heart and aorta. Thus, no major invasive surgery is necessary to usethe present invention. In some circumstances, the present invention alsolessens the hemodynamic burden on the heart by reducing the pressure atthe aortic root during systole.

With reference to FIG. 2, a first embodiment of the present invention 10is shown applied to a patient 12 having an ailing heart 14 and an aorta16, from which peripheral brachiocephalic blood vessels extend,including the right subdlavian 18, the right carotid 20, the leftcarotid 22, and the left axillary 24. Extending from the descendingaorta is another set of peripheral blood vessels, the left and rightfemoral arteries 26, 28.

The first embodiment 10 comprises a pump 32 having an inlet 34 and anoutlet 36 for connection of flexible conduits thereto. The pump 32 ispreferably a rotary pump, either an axial type or a centrifugal type,although other types of pumps may be used, whethercommercially-available or customized. In either case, the pump should besufficiently small to be implanted subcutaneously and preferablyextrathoracically, for example in the groin area of the patient, withoutthe need for major invasive surgery. Because the present invention is anextracardiac system, no valves are necessary. Any inadvertent backflowthrough the pump and/or through the inflow conduit would not harm thepatient.

Regardless of the style chosen, the pump 32 of the present invention issized to pump blood at subcardiac volumetric rates, less than about 50%of the flow rate of an average healthy heart, although flow rates abovethat may be effective. Thus, the pump 32 of the present invention issized and configured to discharge blood at volumetric flow ratesanywhere in the range of 0.1 to 3 liters per minute, depending upon theapplication desired and/or the degree of need for heart assist. Forexample, for a patient experiencing advanced congestive heart failure,it may be preferable to employ a pump that has an average subcardiacrate of 2.5 to 3 liters per minute. In other patients, particularlythose with minimal levels of heart failure, it may be preferable toemploy a pump that has an average subcardiac rate of 0.5 liters perminute or less.

In one embodiment, the pump selected is a continuous flow pump so thatblood perfusion through the circulation system is continuous. In analternative embodiment, the pump selected has the capability ofsynchronous actuation; i.e., it may be actuated in a pulsatile mode,either in copulsating or counterpulsating fashion.

For copulsating action, it is contemplated that the pump 32 would beactuated to discharge blood generally during systole, beginningactuation, for example, during isovolumic contraction before the aorticvalve opens or as the aortic valve opens. The pump would be static whilethe aortic valve is closed following systole, ceasing actuation, forexample, when the aortic valve closes.

For counterpulsating actuation, it is contemplated that the pump 32would be actuated generally during diastole, ceasing actuation, forexample, before or during isovolumic contraction. Such an applicationwould permit and/or enhance coronary blood perfusion. In thisapplication, it is contemplated that the pump would be static during thebalance of systole after the aortic valve is opened, to lessen theburden against which the heart must pump. The aortic valve being openencompasses the periods of opening and closing, wherein blood is flowingtherethrough.

It should be recognized that the designations copulsating andcounterpulsating are general identifiers and are not limited to specificpoints in the patient's heart cycle when the pump begins anddiscontinues actuation. Rather, they are intended to generally refer topump actuation in which the pump is actuating, at least in part, duringsystole and diastole, respectively. For example, it is contemplated thatthe pump might be activated to be out of phase from true copulsating orcounterpulsating actuation described herein, and still be synchronous,depending upon the specific needs of the patient or the desired outcome.One might shift actuation of the pump to begin prior to or afterisovolumic contraction or to begin before or after isovolumic expansion.

Furthermore, the pulsatile pump may be actuated to pulsateasynchronously with the patient's heart Typically, where the patient'sheart is beating irregularly, there may be a desire to pulsate the pumpasynchronously so that the perfusion of blood by the extracardiacpumping system is more regular and, thus, more effective at oxygenatingthe organs. Where the patient's heart beats regularly, but weakly,synchronous pulsation of the extracardiac pump may be preferred.

The pump 32 is driven by an electric motor 40 and is controlledpreferably by a programmable controller 42 that is capable of actuatingthe pump in pulsatile fashion, where desired, and also of controllingthe speed of the pump. For synchronous control, the patient's heartwould preferably be monitored with an EKG in which feedback would beprovided the controller 42. The controller 42 is preferably programmedby the use of external means. This may be accomplished, for example,using RF telemetry circuits of the type commonly used within implantablepacemakers and defibrillator. The controller may also be autoregulatingto permit automatic regulation of the speed, and/or regulation of thesynchronous or a synchronous pulsation of the pump, based upon feedbackfrom ambient sensors monitoring parameters, such as pressure or thepatient's EKG. It is also contemplated that a reverse-direction pump beutilized, if desired, in which the controller is capable of reversingthe direction of either the motor or the impellers of the pump. Such apump might be used where it is desirable to have the option of reversingthe direction of circulation between two peripheral blood vessels.

Power to the motor 40 and controller 42 is provided by a battery 44 thatis preferably rechargeable by an external induction source (not shown),such as an RF induction coil that may be electromagnetically coupled tothe battery to induce a charge therein. The pump can be temporarilystopped during recharging with no appreciable life threatening effect,because the system only supplements the heart, rather than substitutingfor the heart.

While the controller 42 and battery 44 are preferably pre-assembled tothe pump 32 and implanted therewith, it is also contemplated that thepump 32 and motor 40 be implanted at one location and the controller 42and battery 44 be implanted in a separate location. In one alternativearrangement, the pump 32 may be driven externally through a percutaneousdrive line. In another alternative, the pump, motor and controller maybe implanted and powered by an extracorporeal battery. In the lattercase, the battery could be attached to the side of the patient to permitfully ambulatory movement.

The inlet 34 of the pump 32 is preferably connected to a flexible inflowconduit 50 and a flexible outflow conduit 52 to direct blood flow fromone peripheral blood vessel to another. The inflow and outflow conduits50, 52 may, for example, be formed from Dacron, Hemashield or Gortexmaterials, although other materials may be suitable. In some cases, theinflow and/or outflow conduits may come commercially already attached tothe pump. Where it is desired to implant the pump 32 and the conduits50, 52, it is preferably that the inner diameter of the conduits be lessthan 25 mm, although diameters slightly larger may be effective.

In one preferred application of the present invention, the firstembodiment is applied in an arterial-arterial fashion; for example, as afemoral-axillary bypass, as is shown in FIG. 2. It should be appreciatedby one of ordinary skill in the art that an axillary-femoral bypasswould also be effective using the embodiments described herein. Indeed,it should be recognized by one of ordinary skill in the art that thepresent invention might be applied to any of the peripheral bloodvessels in the patient.

The inflow conduit 50 has a first proximal end 56 that connects with theinlet 34 of the pump 32 and a second distal end 58 that connects with afirst peripheral blood vessel, which is preferably the left femoralartery 26 of the patient 12, although the right femoral artery or anyother peripheral artery may be acceptable. In one application, theconnection between the inflow conduit 50 and the first blood vessel isvia an end-to-side anastomosis, although a side-to-side anastomosisconnection might be used mid-stream of the conduit where the inflowconduit were connected at its second end to an additional blood vessel(not shown).

Similarly, the outflow conduit 52 has a first proximal end 62 thatconnects to the outlet 36 of the pump 32 and a second distal end 64 thatconnects with a second peripheral blood vessel, preferably the leftaxillary artery 24 of the patient 12, although the right axillaryartery, or any other peripheral artery, would be acceptable. In oneapplication, the connection between the outflow conduit 52 and thesecond blood vessel is via an end-to-side anastomosis, although aside-to-side anastomosis connection might be used mid-stream of theconduit where the outflow conduit were connected at its second end toyet another blood vessel (not shown). Preferably, the outflow conduit isattached to the second blood vessel at an angle that results in thepredominant flow of blood out of the pump proximally toward the aortaand heart, such as is shown in FIG. 2.

It is preferred that application of the present invention to theperipheral blood vessels be accomplished subcutaneously; i.e., at ashallow depth just below the skin or first muscle layer so as to avoidmajor invasive surgery. It is also preferred that the present inventionbe applied extrathoracically to avoid the need to invade the patient'schest cavity.

Where desired, the entire extracardiac system of the present invention10 may be implanted within the patient 12. In that case, the pump 32 maybe implanted, for example, into the groin area, with the inflow conduit50 connected subcutaneously to, for example, the femoral artery 26proximate the pump 32. The outflow conduit would be tunnelledsubcutaneously through to, for example, the left axillary artery 24. Inan alternative arrangement, the pump 32 and associated drive andcontroller could be temporarily fastened to the exterior skin of thepatient, with the inflow and outflow conduits 50, 52 connectedpercutaneously. In either case, the patient may be ambulatory withoutrestriction of tethered lines.

It is contemplated that, where an anastomosis connection is not desired,a special connector may be used to connect the conduits 50, 52 to theperipheral blood vessels. With reference to FIG. 3, a second embodimentof the present invention is shown, wherein the inflow conduit 50 andoutflow conduit 52 are connected to the peripheral blood vessels viafirst and second connectors 68, 70 each comprising three-openingfittings. In the preferred embodiment, the connectors 68, 70 comprise anintra-vascular, generally-tee-shaped fitting 72 having a proximal end74, a distal end 76, and an angled divergence 78 permitting connectionto the inflow and outflow conduits 50, 52 and the blood vessels. Theproximal and distal ends 74, 76 of the fittings 72 permit connection tothe blood vessel into which the fitting is positioned. The angle of thedivergence 78 of the fittings 72 may be 90 degrees or less from the axisof flow through the blood vessel. In another embodiment, the connectors68, 70 are sleeves (not shown) that surround and attach to the outsideof the peripheral blood vessel where, within the interior of the sleeve,a port to the blood vessel is provided to permit blood flow from theconduits 50, 52 when they are connected to the connectors 68, 70,respectively. Other types of connectors having other configurations arecontemplated that may avoid the need for an anastomosis connection orthat permit connection of the conduits to the blood vessels. It iscontemplated that a connection to the blood vessels might be made via acannula, wherein the cannula is implanted, along with the inflow andoutflow conduits.

The advantage of discrete connectors is their potential application topatients with chronic CHF. A connector eliminates a need for ananastomosis connection between the conduits of the present inventionsystem and the peripheral blood vessels where it is desired to removeand/or replace the system more than one time. The connectors could beapplied to the first and second blood vessels semi-permanently, with anend cap applied to the divergence for later quick-connection of thepresent invention system to the patient. In this regard, a patient mightexperience the benefit of the present invention periodically, withouthaving to reconnect and redisconnect the conduits from the blood vesselsvia an anastomosis procedure each time. Each time it is desired toimplement the present invention, the end caps would be removed and theconduit attached to the connectors quickly.

In the preferred embodiment of the connector 70, the divergence 78 isoriented at an acute angle significantly less than 90° from the axis ofthe fitting 72, as shown in FIG. 3, so that a majority of the bloodflowing through the outflow conduit 52 into the blood vessel (e.g., leftaxillary 24) flows in a direction proximally toward the heart 14, ratherthan in the distal direction. In an alternative embodiment, the proximalend 74 of the fitting 72 may have a diameter larger than the diameter ofthe distal end 76, without need of having an angled divergence, toachieve the same result.

With or without a connector, with blood flow directed proximally towardthe aorta, the result may be concurrent flow down the descending aorta,which will result in the reduction of pressure at the aortic root. Thus,the present invention may be applied so to reduce the afterload on thepatient's heart, permitting at least partial if not complete CHFrecovery, while supplementing blood circulation. Concurrent flow dependsupon the phase of operation of the pulsatile pump and the choice ofsecond blood vessel to which the outflow conduit is connected.

While the present invention may be applied to create anarterial-arterial bypass, given the nature of the present invention,i.e., supplementation of circulation to meet organ demand, avenous-arterial bypass may also be used. For example, with reference toFIG. 4, one embodiment of the present invention 10 may be applied to thepatient 12 such that the inflow conduit 50 is connected to a peripheralvein, such as the left femoral vein 80. In this arrangement, the outflowconduit 50 may be connected to one of the peripheral arteries, such asthe left axillary 24. Arterial-venous arrangements are contemplated aswell. In those venous-arterial cases where the inflow is connected to avein and the outflow is connected to an artery, the pump 32 should besized to permit flow sufficiently small so that oxygen-deficient blooddoes not rise to unacceptable levels in the arteries. It should beappreciated that the connections to the peripheral veins could be by oneor more methods described above for connecting to a peripheral artery.It should also be appreciated that the present invention could beapplied as a venous-venous bypass, wherein the inflow and outflow areconnected to separate peripheral veins. In addition, an alternativeembodiment comprises two discrete pumps and conduit arrangements, onebeing applied as a venous-venous bypass, and the other as anarterial-arterial bypass.

A partial external application of the present invention is contemplatedwhere a patient's heart failure is acute; i.e., is not expected to lastlong, or in the earlier stages of heart failure (where the patient is inNew York Heart Association Classification (NYHAC) functional classes IIor III). With reference to FIG. 5, a third embodiment of the presentinvention 110 is applied percutaneously to a patient 112 to bypassbetween two peripheral blood vessels wherein a pump 132 and itsassociated motor and controls are employed extracorporeally. The pump132 has an inflow conduit 150 and an outflow conduit 152 associatedtherewith for connection to two peripheral blood vessels. The inflowconduit 150 has a first end 156 and second end 158 wherein the secondend is connected to a first peripheral blood vessel (e.g., femoralartery 126) by way of a cannula 180. The cannula 180 has a first end 182sealably connected to the second end 158 of the inflow conduit 150. Thecannula 180 also has a second end 184 used to pierce the skin or firstlayer of muscle through surgical opening 186 and to pierce the bloodvessel source (e.g., femoral artery 126).

Simnilarly, the outflow conduit 152 has a first end 162 and second end164 wherein the second end is connected to a second peripheral bloodvessel (e.g., left axillary artery 124) by way of a cannula 180. Likethe inflow cannula, the outflow cannula 180 has a first end 182 sealablyconnected to the second end 164 of the outflow conduit 152. The outflowcannula 180 also has a second end 184 used to pierce the skin or firstlayer of muscle through surgical opening 190 and to pierce the secondblood vessel (e.g., left axillary artery 124). By use of a percutaneousapplication, the present invention may be applied temporarily withoutthe need to implant any aspect thereof or to make anastomosisconnections to the blood vessels.

An alternative variation of the third embodiment may be used where it isdesired to treat a patient periodically, but for short periods of timeeach occasion and without the use of special connectors. With thisvariation, it is contemplated that the second ends of the inflow andoutflow conduits be more permanently connected to the associated bloodvessels via, for example, an anastomosis connection, wherein a portionof each conduit proximate to the blood vessel connection is implantedpercutaneously with a removable cap enclosing the eternally-exposedfirst end (or an intervening end thereof) of the conduit external to thepatient. When it is desired to provide a circulatory bypass tosupplement blood flow, the removable cap on each exposedpercutaneously-positioned conduit could be removed and the pump (or thepump with a length of inflow and/or outflow conduit attached thereto)inserted between the exposed percutaneous conduits. In this regard, apatient may experience the benefit of the present inventionperiodically, without having to reconnect and redisconnect the conduitsfrom the blood vessels each time.

Another embodiment of the present invention includes a plurality ofinflow and/or outflow conduits. For example, with reference to FIG. 6, afourth embodiment of the present invention 210 includes a pump 232 influid communication with a plurality of inflow conduits 250A, 250B and aplurality of outflow conduits 252A, 252B. Each pair of conduitsconverges at a generally Y-shaped convergence 296 that converges theflow at the inflow end and diverges the flow at the outflow end. Eachconduit may be connected to a separate peripheral blood vessel, althoughit is possible to have two connections to the same blood vessel atremote locations. In one arrangement, all four conduits are connected toperipheral arteries. Alternatively, one or more of the conduits could beconnected to veins. In the application shown in FIG. 6, inflow conduit250A is connected to left femoral artery 226 while inflow conduit 250Bis connected to left femoral vein 278. Outflow conduit 252A is connectedto left axillary artery 224 while outflow conduit 252B is connected toleft carotid artery 222. It should be noted that the connections of anyor all of the conduits to the blood vessels may be via an anastomosisconnection or via a special connector, as described above. In addition,the embodiment of FIG. 6 may be applied to any combination of peripheralblood vessels that would best suit the patient's condition. For example,it may be desired to have one inflow conduit and two outflow conduits orvice versa. Finally, it should be noted that more than two conduits maybe used on the inflow or outflow side, where the number of inflowconduits is not necessarily equal to the number of outflow conduits.

While the above description has explained the inventive features of theinvention as applied to various embodiments, it will be understood thatthe variations in the form and details of the apparatus or method may bemade by those of ordinary skill in the art without departing from thespirit of the invention. The scope of the invention is indicated by theappended claims herein, however, not by the foregoing description.

What is claimed is:
 1. A method for supplementing the circulation ofblood through a patient without connecting any component to thepatient's heart, the method comprising the steps of: connecting a distalend of an inflow conduit of a rotary pump to a first blood vessel thatis not a primary blood vessel with a conduit having an inner diameter nogreater than about 25 millimeters using a minimally invasive surgicalprocedure to permit the flow of blood to the pump from the first bloodvessel, said pump configured to pump blood at volumetric rates that areon average subcardiac; connecting a distal end of an outflow conduit ofthe pump to a second blood vessel that is not a primary blood vesselwith a conduit having an inner diameter no greater than about 25millimeters using a minimally invasive surgical procedure to permit theflow of blood away from the pump to the second blood vessel, wherein thestep of connecting the inflow conduit to the first blood vesselcomprises using an end-to-side anastomosis connection; and operatingsaid pump to perfuse blood through the patient's circulatory system atvolumetric rates that are on average subcardiac.
 2. A method forsupplementing the circulation of blood through a patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a rotarypump to a first blood vessel that is not a primary blood vessel with aconduit having an inner diameter no greater than about 25 millimetersusing a minimally invasive surgical procedure to permit the flow ofblood to the pump from the first blood vessel, said pump configured topump blood at volumetric rates that are on average subcardiac;connecting a distal end of an outflow conduit of the pump to a secondblood vessel that is not a primary blood vessel with a conduit having aninner diameter no greater than about 25 millimeters using a minimallyinvasive surgical procedure to permit the flow of blood away from thepump to the second blood vessel, wherein the step of connecting theinflow conduit to the first blood vessel comprises using a cannula; andoperating said pump to perfuse blood through the patient's circulatorysystem at volumetric rates that are on average subcardiac.
 3. The methodof claim 2 wherein the cannula projects into the blood vessel so as todraw blood from a point upstream of the point of blood vesselpenetration.
 4. A method for supplementing the circulation of bloodthrough a patient without connecting any component to the patient'sheart, the method comprising the steps of: connecting a distal end of aninflow conduit of a rotary pump to a first blood vessel that is not aprimary blood vessel with a conduit having an inner diameter no greaterthan about 25 millimeters using a minimally invasive surgical procedureto permit the flow of blood to the pump from the first blood vessel,said pump configured to pump blood at volumetric rates that are onaverage subcardiac; connecting a distal end of an outflow conduit of thepump to a second blood vessel that is not a primary blood vessel with aconduit having an inner diameter no greater than about 25 millimetersusing a minimally invasive surgical procedure to permit the flow ofblood away from the pump to the second blood vessel; and operating saidpump to perfuse blood through the patient's circulatory system atvolumetric rates that are on average subcardiac, wherein the step ofoperating the pump comprises actuating the pump in a generallycounterpulsating pulsatile fashion.
 5. A method for supplementing thecirculation of blood through a patient without connecting any componentto the patient's heart, the method comprising the steps of: connecting adistal end of an inflow conduit of a rotary pump to a first blood vesselthat is not a primary blood vessel with a conduit having an innerdiameter no greater than about 25 millimeters using a minimally invasivesurgical procedure to permit the flow of blood to the pump from thefirst blood vessel, said pump configured to pump blood at volumetricrates that are on average subcardiac; connecting a distal end of anoutflow conduit of the pump to a second blood vessel that is not aprimary blood vessel with a conduit having an inner diameter no greaterthan about 25 millimeters using a minimally invasive surgical procedureto permit the flow of blood away from the pump to the second bloodvessel; and operating said pump to perfuse blood through the patient'scirculatory system at volumetric rates that are on average subcardiac,wherein the step of operating the pump comprises actuating the pump in apulsatile fashion so as to reduce the pressure at the aortic root.
 6. Amethod for supplementing the circulation of blood through a patientwithout connecting any component to the patient's heart, the methodcomprising the steps of: connecting a distal end of an inflow conduit ofa rotary pump to a first blood vessel that is not a primary blood vesselwith a conduit having an inner diameter no greater than about 25millimeters using a minimally invasive surgical procedure to permit theflow of blood to the pump from the first blood vessel, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa second blood vessel that is not a primary blood vessel with a conduithaving an inner diameter no greater than about 25 millimeters using aminimally invasive surgical procedure to permit the flow of blood awayfrom the pump to the second blood vessel; and operating said pump toperfuse blood through the patient's circulatory system at volumetricrates that are on average subcardiac, wherein the pump is actuated in acontinuous fashion so as to reduce the pressure at the aortic root.
 7. Amethod for supplementing the circulation of blood through a patientwithout connecting any component to the patient's heart, the methodcomprising the steps of: connecting a distal end of an inflow conduit ofa rotary pump to a first blood vessel that is not a primary blood vesselwith a conduit having an inner diameter no greater than about 25millimeters using a minimally invasive surgical procedure to permit theflow of blood to the pump from the first blood vessel, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa second blood vessel that is not a primary blood vessel with a conduithaving an inner diameter no greater than about 25 millimeters using aminimally invasive surgical procedure to permit the flow of blood awayfrom the pump to the second blood vessel, wherein the step of connectingthe outflow conduit to the second blood vessel comprises using anend-to-side anastomosis connection; and operating said pump to perfuseblood through the patient's circulatory system at volumetric rates thatare on average subcardiac.
 8. A method for supplementing the circulationof blood through a patient without connecting any component to thepatient's heart, the method comprising the steps of: connecting a distalend of an inflow conduit of a rotary pump to a first blood vessel thatis not a primary blood vessel with a conduit having an inner diameter nogreater than about 25 millimeters using a minimally invasive surgicalprocedure to permit the flow of blood to the pump from the first bloodvessel, said pump configured to pump blood at volumetric rates that areon average subcardiac; connecting a distal end of an outflow conduit ofthe pump to a second blood vessel that is not a primary blood vesselwith a conduit having an inner diameter no greater than about 25millimeters using a minimally invasive surgical procedure to permit theflow of blood away from the pump to the second blood vessel, wherein thestep of connecting the outflow conduit to the second blood vesselcomprises using a cannula; and operating said pump to perfuse bloodthrough the patient's circulatory system at volumetric rates that are onaverage subcardiac.
 9. The method of claim 8 wherein the cannulaprojects into the blood vessel so as to direct blood to a pointdownstream of the point of blood vessel penetration.
 10. A method forsupplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toa first artery that is not the aorta or pulmonary artery with a cannulausing a minimally invasive surgical procedure to permit the flow ofblood to the pump from the first artery, said pump configured to pumpblood at volumetric rates that are on average subcardiac; connecting adistal end of an outflow conduit of the pump to a second artery that isnot the aorta or pulmonary artery using a minimally invasive surgicalprocedure to permit the flow of blood away from the pump to the secondartery; and operating said pump to perfuse blood through the patient'scirculatory system at volumetric rates that are on average subcardiac.11. A method for supplementing the circulation of blood through thepatient without connecting any component to the patient's heart, themethod comprising the steps of: connecting a distal end of an inflowconduit of a pump to a first artery that is not the aorta or pulmonaryartery with an end-to-side anastomosis using a minimally invasivesurgical procedure to permit the flow of blood to the pump from thefirst artery, said pump configured to pump blood at volumetric ratesthat are on average subcardiac; connecting a distal end of an outflowconduit of the pump to a second artery that is not the aorta orpulmonary artery using a minimally invasive surgical procedure to permitthe flow of blood away from the pump to the second artery; and operatingsaid pump to perfuse blood through the patient's circulatory system atvolumetric rates that are on average subcardiac.
 12. A method forsupplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toa first artery that is not the aorta or pulmonary artery using aminimally invasive surgical procedure to permit the flow of blood to thepump from the first artery, said pump configured to pump blood atvolumetric rates that are on average subcardiac; connecting a distal endof an outflow conduit of the pump to a second artery that is not theaorta or pulmonary artery with a cannula using a minimally invasivesurgical procedure to permit the flow of blood away from the pump to thesecond artery; and operating said pump to perfuse blood through thepatient's circulatory system at volumetric rates that are on averagesubcardiac.
 13. A method for supplementing the circulation of bloodthrough the patient without connecting any component to the patient'sheart, the method comprising the steps of: connecting a distal end of aninflow conduit of a pump to a first artery that is not the aorta orpulmonary artery using a minimally invasive surgical procedure to permitthe flow of blood to the pump from the first artery, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa second artery that is not the aorta or pulmonary artery with anend-to-side anastomosis using a minimally invasive surgical procedure topermit the flow of blood away from the pump to the second artery; andoperating said pump to perfuse blood through the patient's circulatorysystem at volumetric rates that are on average subcardiac.
 14. A methodfor supplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toan axillary artery using a minimally invasive surgical procedure topermit the flow of blood to the pump from the axillary artery, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa second artery using a minimally invasive surgical procedure to permitthe flow of blood away from the pump to the second artery; and operatingsaid pump to perfuse blood through the patient's circulatory system atvolumetric rates that are on average subcardiac.
 15. A method forsupplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toa first artery that is not the aorta or pulmonary artery using aminimally invasive surgical procedure to permit the flow of blood to thepump from the first artery, said pump configured to pump blood atvolumetric rates that are on average subcardiac; connecting a distal endof an outflow conduit of the pump to an axillary artery using aminimally invasive surgical procedure to permit the flow of blood awayfrom the pump to the axillary artery; and operating said pump to perfuseblood through the patient's circulatory system at volumetric rates thatare on average subcardiac.
 16. A method for supplementing thecirculation of blood through the patient without connecting anycomponent to the patient's heart, the method comprising the steps of:connecting a distal end of an inflow conduit of a pump to a femoralartery using a minimally invasive surgical procedure to permit the flowof blood to the pump from the femoral artery, said pump configured topump blood at volumetric rates that are on average subcardiac;connecting a distal end of an outflow conduit of the pump to a secondartery that is not the aorta or pulmonary artery using a minimallyinvasive surgical procedure to permit the flow of blood away from thepump to the second artery; and operating said pump to perfuse bloodthrough the patient's circulatory system at volumetric rates that are onaverage subcardiac.
 17. A method for supplementing the circulation ofblood through the patient without connecting any component to thepatient's heart, the method comprising the steps of: connecting a distalend of an inflow conduit of a pump to a first artery that is not theaorta or pulmonary artery using a minimally invasive surgical procedureto permit the flow of blood to the pump from the first artery, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa femoral artery using a minimally invasive surgical procedure to permitthe flow of blood away from the pump to the femoral artery; andoperating said pump to perfuse blood through the patient's circulatorysystem at volumetric rates that are on average subcardiac.
 18. A methodfor supplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toan iliac artery using a minimally invasive surgical procedure to permitthe flow of blood to the pump from the iliac artery, said pumpconfigured to pump blood at volumetric rates that are on averagesubcardiac; connecting a distal end of an outflow conduit of the pump toa second artery that is not the aorta or pulmonary artery using aminimally invasive surgical procedure to permit the flow of blood awayfrom the pump to the second artery; and operating said pump to perfuseblood through the patient's circulatory system at volumetric rates thatare on average subcardiac.
 19. A method for supplementing thecirculation of blood through the patient without connecting anycomponent to the patient's heart, the method comprising the steps of:connecting a distal end of an inflow conduit of a pump to a first arterythat is not the aorta or pulmonary artery using a minimally invasivesurgical procedure to permit the flow of blood to the pump from thefirst artery, said pump configured to pump blood at volumetric ratesthat are on average subcardiac; connecting a distal end of an outflowconduit of the pump to an iliac artery using a minimally invasivesurgical procedure to permit the flow of blood away from the pump to theiliac artery; and operating said pump to perfuse blood through thepatient's circulatory system at volumetric rates that are on averagesubcardiac.
 20. A method for supplementing the circulation of bloodthrough the patient without connecting any component to the patient'sheart, the method comprising the steps of: connecting a distal end of aninflow conduit of a pump to a subdlavian artery using a minimallyinvasive surgical procedure to permit the flow of blood to the pump fromthe subclavian artery, said pump configured to pump blood at volumetricrates that are on average subcardiac; connecting a distal end of anoutflow conduit of the pump to a second artery that is not the aorta orpulmonary artery using a minimally invasive surgical procedure to permitthe flow of blood away from the pump to the second artery; and operatingsaid pump to perfuse blood through the patient's circulatory system atvolumetric rates that are on average subcardiac.
 21. A method forsupplementing the circulation of blood through the patient withoutconnecting any component to the patient's heart, the method comprisingthe steps of: connecting a distal end of an inflow conduit of a pump toa first artery that is not the aorta or pulmonary artery using aminimally invasive surgical procedure to permit the flow of blood to thepump from the first artery, said pump configured to pump blood atvolumetric rates that are on average subcardiac; connecting a distal endof an outflow conduit of the pump to a subclavian artery using aminimally invasive surgical procedure to permit the flow of blood awayfrom the pump to the subclavian artery; and operating said pump toperfuse blood through the patient's circulatory system at volumetricrates that are on average subcardiac.
 22. An extracardiac pumping systemfor supplementing blood circulation through a patient without anycomponent thereof being connected to the patient's heart, theextracardiac system comprising: a rotary pump configured to pump bloodthrough the patient at subcardiac volumetric rates, said pump having anaverage flow rate that, during normal operation thereof, issubstantially below that of the patient's heart when healthy; an inflowconduit having an inner diameter that is no greater than 25 millimetersfluidly coupled to the pump to direct blood to the pump from a firstblood vessel that is not a primary vessel, the inflow conduit having afirst end configured to couple to the first blood vessel; an outflowconduit having an inner diameter that is no greater than 25 millimetersfluidly coupled to the pump to direct blood from the pump to a secondblood vessel that is not a primary vessel, the outflow conduit having afirst end configured to couple to the second blood vessel; and at leastone additional inflow conduit having a first end configured to connectto a blood vessel that is not a primary vessel.
 23. An extracardiacpumping system for supplementing blood circulation through a patientwithout any component thereof being connected to the patient's heart,the extracardiac system comprising: a continuous-flow pump configured topump blood through the patient at subcardiac volumetric rates, said pumphaving an average flow rate that, during normal operation thereof, issubstantially below that of the patient's heart when healthy; an inflowconduit having an inner diameter that is no greater than 25 millimetersfluidly coupled to the pump to direct blood to the pump from a firstblood vessel that is not a primary vessel, the inflow conduit having afirst end configured to couple to the first blood vessel; and, anoutflow conduit having an inner diameter that is no greater than 25millimeters fluidly coupled to the pump to direct blood from the pump toa second blood vessel that is not a primary vessel, the outflow conduithaving a first end configured to couple to the second blood vessel.